Optical semiconductor device with integrated dies

ABSTRACT

The present application discloses an optical semiconductor device. The optical semiconductor device includes a logic die, a memory die, and a sensor die. The logic die includes a front surface. The memory die includes a front surface positioned on the front surface of the logic die, and a back surface opposite to the front surface of the memory die. The sensor die includes a front surface positioned on the back surface of the memory die, a back surface opposite to the front surface of the sensor die, a sensor unit located at the back surface of the sensor die, a color filter positioned on the back surface of the sensor die, and a micro-lens positioned on the color filter.

TECHNICAL FIELD

The present disclosure relates to an optical semiconductor device, andmore particularly, to an optical semiconductor device with integrateddies.

DISCUSSION OF THE BACKGROUND

Optical semiconductor devices are used in a variety of electronicapplications, such as personal computers, cellular telephones, digitalcameras, and other electronic equipment. The dimensions of opticalsemiconductor devices are continuously being scaled down to meet theincreasing demand of computing ability. However, a variety of issuesarise during the scaling-down process, and such issues are continuouslyincreasing. Therefore, challenges remain in achieving improved quality,yield, performance, and reliability and reduced complexity.

This Discussion of the Background section is provided for backgroundinformation only. The statements in this Discussion of the Backgroundare not an admission that the subject matter disclosed in this sectionconstitutes prior art to the present disclosure, and no part of thisDiscussion of the Background section may be used as an admission thatany part of this application, including this Discussion of theBackground section, constitutes prior art to the present disclosure.

SUMMARY

One aspect of the present disclosure provides an optical semiconductordevice including a logic die including a core circuit area and a logicperipheral circuit area; a memory die positioned on the logic die andincluding a memory cell area and a memory peripheral area, and a firstinter-die via positioned in the memory peripheral area and electricallyconnected to the logic peripheral circuit area; and a sensor diepositioned on the memory die and including a sensor pixel area and asensor peripheral area, a first intra-die via positioned in the sensorperipheral area and electrically coupled to the logic peripheral circuitarea through the first inter-die via, and a second intra-die viapositioned in the sensor peripheral area. A height of the firstintra-die via is greater than a height of the second intra-die via.

Another aspect of the present disclosure provides an opticalsemiconductor device including a logic die including a front surface; amemory die including a front surface positioned on the front surface ofthe logic die, and a back surface opposite to the front surface of thememory die; and a sensor die including a front surface positioned on theback surface of the memory die, a back surface opposite to the frontsurface of the sensor die, a sensor unit located at the back surface ofthe sensor die, a color filter positioned on the back surface of thesensor die, and a micro-lens positioned on the color filter.

Another aspect of the present disclosure provides an opticalsemiconductor device including a logic die including a core circuit areaand a logic peripheral circuit area; a memory die positioned on thelogic die and including a memory cell area and a memory peripheral area;a first inter-die via positioned in the memory peripheral area; alanding pad positioned on the first inter-die via; and a sensor diepositioned on the memory die and including a sensor pixel area and asensor peripheral area, a first intra-die via positioned in the sensorperipheral area. The first inter-die via and the first intra-die via areelectrically coupled through the landing pad in a cascade manner.

Due to the design of the optical semiconductor device of the presentdisclosure, by employing the first inter-die via, the first intra-dievia, and the second intra-die via, the signal produced in the sensor diemay be transferred to the functional circuits of the logic die toperform various processing which usually needs complicated circuits.That is, the sensor die can only reserve the essential elements foroptical sensing function so that the complexity of fabrication of thesensor die may be simplified. As a result, the yield of the opticalsemiconductor device may be improved. In addition, the first inter-dievia, the first intra-die via, and the second intra-die via may alsoshorten the signal path between the function circuits of different diesso that the energy consumption for signal transferring may be reduced.Furthermore, by further integrating the memory die, the intermediateprocessing or the post processing signal may be easily stored.

The foregoing has outlined rather broadly the features and technicaladvantages of the present disclosure in order that the detaileddescription of the disclosure that follows may be better understood.Additional features and advantages of the disclosure will be describedhereinafter, and form the subject of the claims of the disclosure. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present disclosure. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the disclosure as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates, in a flowchart diagram form, a method forfabricating an optical semiconductor device in accordance with oneembodiment of the present disclosure;

FIGS. 2 to 6 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device inaccordance with one embodiment of the present disclosure;

FIG. 7 illustrates, in a schematic close-up cross-sectional viewdiagram, a first inter-die via of the optical semiconductor device inaccordance with one embodiment of the present disclosure;

FIGS. 8 to 15 are schematic cross-sectional view diagrams illustratingpart of the flow for fabricating the optical semiconductor device inaccordance with one embodiment of the present disclosure;

FIG. 16 illustrates, in a schematic cross-sectional view diagram, anoptical semiconductor device in accordance with another embodiment ofthe present disclosure;

FIGS. 17 and 18 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device inaccordance with another embodiment of the present disclosure;

FIGS. 19 to 21 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device inaccordance with another embodiment of the present disclosure;

FIGS. 22 to 29 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device inaccordance with another embodiment of the present disclosure;

FIGS. 30 and 31 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device inaccordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

It should be understood that when an element or layer is referred to asbeing “connected to” or “coupled to” another element or layer, it can bedirectly connected to or coupled to another element or layer, orintervening elements or layers may be present.

It should be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. Unless indicated otherwise, these terms areonly used to distinguish one element from another element. Thus, forexample, a first element, a first component or a first section discussedbelow could be termed a second element, a second component or a secondsection without departing from the teachings of the present disclosure.

Unless the context indicates otherwise, terms such as “same,” “equal,”“planar,” or “coplanar,” as used herein when referring to orientation,layout, location, shapes, sizes, amounts, or other measures do notnecessarily mean an exactly identical orientation, layout, location,shape, size, amount, or other measure, but are intended to encompassnearly identical orientation, layout, location, shapes, sizes, amounts,or other measures within acceptable variations that may occur, forexample, due to manufacturing processes. The term “substantially” may beused herein to reflect this meaning. For example, items described as“substantially the same,” “substantially equal,” or “substantiallyplanar,” may be exactly the same, equal, or planar, or may be the same,equal, or planar within acceptable variations that may occur, forexample, due to manufacturing processes.

In the present disclosure, an optical semiconductor device generallymeans a device which can function by utilizing semiconductorcharacteristics, and an electro-optic device, a light-emitting displaydevice, a semiconductor circuit, and an electronic device are allincluded in the category of the optical semiconductor device.

It should be noted that, in the description of the present disclosure,above (or up) corresponds to the direction of the arrow of the directionZ, and below (or down) corresponds to the opposite direction of thearrow of the direction Z.

FIG. 1 illustrates, in a flowchart diagram form, a method 10 forfabricating an optical semiconductor device 1A in accordance with oneembodiment of the present disclosure. FIGS. 2 to 6 are schematiccross-sectional view diagrams illustrating part of a flow forfabricating the optical semiconductor device 1A in accordance with oneembodiment of the present disclosure. FIG. 7 illustrates, in a schematicclose-up cross-sectional view diagram, a first inter-die via 401 of theoptical semiconductor device 1A in accordance with one embodiment of thepresent disclosure. FIGS. 8 to 15 are schematic cross-sectional viewdiagrams illustrating part of the flow for fabricating the opticalsemiconductor device 1A in accordance with one embodiment of the presentdisclosure.

With reference to FIGS. 1 and 2 , at step S11, a logic die 100 may beprovided.

With reference to FIG. 2 , the logic die 100 may include a firstsubstrate 101, a plurality of logic device elements 103, a pluralityfirst conductive features 105, and a first dielectric layer 107.

With reference to FIG. 2 , the first substrate 101 may be a bulksemiconductor substrate. The bulk semiconductor substrate may be formedof, for example, an elementary semiconductor such as silicon orgermanium, or a compound semiconductor such as silicon germanium,silicon carbide, gallium arsenide, gallium phosphide, indium phosphide,indium arsenide, indium antimonide, or other III-V compoundsemiconductor or II-VI compound semiconductor.

In some embodiments, the thickness T1 of the first substrate 101 may bebetween about 500 μm and about 700 μm. For example, the thickness T1 ofthe first substrate 101 may be about 600 μm.

With reference to FIG. 2 , the first substrate 101 may include a corecircuit area LCA and a logic peripheral circuit area LPA. In someembodiments, the logic peripheral circuit area LPA may be next to thecore circuit area LCA. In some embodiments, in a top-view perspective(not shown), the core circuit area LCA may be the central region of thefirst substrate 101. The logic peripheral circuit area LPA may be theperipheral region of the first substrate 101 which is surrounding thecentral region.

It should be noted that, in the description of the present disclosure,the core circuit area LCA may comprise a portion of the first substrate101 and spaces above and under the portion of the first substrate 101.Describing an element as being disposed on the core circuit area LCAmeans that the element is disposed on a top surface of the portion ofthe first substrate 101. Describing an element as being disposed in thecore circuit area LCA means that the element is disposed in the portionof the first substrate 101; however, a top surface of the element may beeven with the top surface of the portion of the first substrate 101.Describing an element as being disposed above the core circuit area LCAmeans that the element is disposed above the top surface of the portionof the first substrate 101. Describing an element as being disposedunder the core circuit area LCA means that the element is disposed underthe bottom surface of the portion of the first substrate 101; whereinthe element contacts the bottom surface of the portion of the firstsubstrate 101 or is distant from the bottom surface of the portion ofthe first substrate 101. Accordingly, the logic peripheral circuit areaLPA may comprise another portion of the first substrate 101 and spacesabove and under the other portion of the first substrate 101.

With reference to FIG. 2 , the logic device elements 103 may be formedon the first substrate 101. Some portions of the logic device elements103 may be formed in the first substrate 101. The logic device elements103 may be transistors such as complementary metal-oxide-semiconductortransistors, metal-oxide-semiconductor field-effect transistors, finfield-effect-transistors, the like, or a combination thereof.

With reference to FIG. 2 , the first dielectric layer 107 may be formedon the first substrate 101. In some embodiments, the first dielectriclayer 107 may be a stacked layer structure. The first dielectric layer107 may include a plurality of insulating sub-layers. Each of theinsulating sub-layers may have a thickness between about 0.5 μm andabout 3.0 μm. The insulating sub-layers may be formed of, for example,silicon oxide, borophosphosilicate glass, undoped silicate glass,fluorinated silicate glass, low-k dielectric materials, the like, or acombination thereof. The insulating sub-layers may be formed ofdifferent materials but are not limited thereto.

The low-k dielectric materials may have a dielectric constant less than3.0 or even less than 2.5. In some embodiments, the low-k dielectricmaterials may have a dielectric constant less than 2.0. The insulatingsub-layers may be formed by deposition processes such as chemical vapordeposition, plasma-enhanced chemical vapor deposition, or the like.Planarization processes may be performed after the deposition processesto remove excess material and provide a substantially flat surface forsubsequent processing steps.

It should be noted that, in the description of present disclosure, theterm “about” modifying the quantity of an ingredient, component, orreactant of the present disclosure employed refers to variation in thenumerical quantity that can occur, for example, through typicalmeasuring and liquid handling procedures used for making concentrates orsolutions. Furthermore, variation can occur from inadvertent error inmeasuring procedures, differences in the manufacture, source, or purityof the ingredients employed to make the compositions or carry out themethods, and the like. In one aspect, the term “about” means within 10%of the reported numerical value. In another aspect, the term “about”means within 5% of the reported numerical value. Yet, in another aspect,the term “about” means within 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of thereported numerical value.

With reference to FIG. 2 , the plurality first conductive features 105may be formed in the first dielectric layer 107. The first conductivefeatures 105 may include first conductive lines 105L, first conductivevias 105V, and first conductive pads 105P. The first conductive lines105L may be separated from each other and may be horizontally disposedin the first dielectric layer 107 along the direction Z. In the presentembodiment, the topmost first conductive lines 105L may be designated asthe first conductive pads 105P. The top surfaces of the first conductivepads 105P and the top surface of the first dielectric layer 107 may besubstantially coplanar. The first conductive vias 105V may connectadjacent first conductive lines 105L along the direction Z, adjacentlogic device element 103 and first conductive line 105L, and adjacentfirst conductive pad 105P and first conductive line 105L. In someembodiments, the first conductive features 105 may be formed of, forexample, tungsten, cobalt, zirconium, tantalum, titanium, aluminum,ruthenium, copper, metal carbides (e.g., tantalum carbide, titaniumcarbide, tantalum magnesium carbide), metal nitrides (e.g., titaniumnitride), transition metal aluminides, or a combination thereof. Thefirst conductive features 105 may be formed during the formation of thefirst dielectric layer 107.

In some embodiments, the logic device elements 103 and the firstconductive features 105 may together configure functional units of theoptical semiconductor device 1A. A functional unit, in the descriptionof the present disclosure, generally refers to functionally relatedcircuitry that has been partitioned for functional purposes into adistinct unit. In some embodiments, the functional units of the logicdie 100 may include, for example, highly complex circuits such asprocessor cores, memory controllers, or accelerator units.

In some embodiments, the functional units of the logic die 100 mayinclude control circuit and high-speed circuitry that are associatedwith the memory die 200 which will be illustrated later.

In some embodiments, the functional units of the logic die 100 mayinclude processor core intellectual properties, analog-to-digitalconverters, digital-to-analog converters, and phase-locked loops.

In some embodiments, the functional units may be located at the corecircuit area LCA. In some embodiments, the functional units may belocated at the core circuit area LCA and the logic peripheral circuitarea LPA.

It should be noted that, in the description of the present disclosure,the term “front” surface is a term of art implying the major surface ofthe structure upon which is formed device elements and conductivefeatures. Likewise, the “back” surface of a structure is that majorsurface opposite to the face. For example, the top surface of the firstdielectric layer 107 may be referred to as the front surface 100F of thelogic die 100. The bottom surface of the first substrate 101 may bereferred to as the back surface 100B of the logic die 100.

It should be noted that, in the description of the present disclosure, asurface of an element (or a feature) located at the highest verticallevel along the direction Z is referred to as a top surface of theelement (or the feature). A surface of an element (or a feature) locatedat the lowest vertical level along the direction Z is referred to as abottom surface of the element (or the feature).

With reference to FIGS. 1 and 3 , at step S13, a memory die 200 may beprovided.

With reference to FIG. 3 , the memory die 200 may include a secondsubstrate 201, a plurality of memory device elements 203, pluralitysecond conductive features 205, a second dielectric layer 207, and aplurality of storage units 209.

With reference to FIG. 3 , the second substrate 201 may be a bulksemiconductor substrate. The bulk semiconductor substrate may be formedof, for example, an elementary semiconductor such as silicon orgermanium, or a compound semiconductor such as silicon germanium,silicon carbide, gallium arsenide, gallium phosphide, indium phosphide,indium arsenide, indium antimonide, or other III-V compoundsemiconductor or II-VI compound semiconductor.

In some embodiments, the thickness T2 of the second substrate 201 may bebetween about 500 μm and about 700 μm. For example, the thickness T2 ofthe second substrate 201 may be about 600 μm.

With reference to FIG. 3 , the second substrate 201 may include a memorycell area MCA and a memory peripheral area MPA. In some embodiments, thememory peripheral area MPA may be next to the memory cell area MCA. Insome embodiments, in a top-view perspective (not shown), the memory cellarea MCA may be the central region of the second substrate 201. Thememory peripheral area MPA may be the peripheral region of the secondsubstrate 201 which is surrounding the central region.

With reference to FIG. 3 , the memory device elements 203 may be formedon the second substrate 201. Some portions of the memory device elements203 may be formed in the second substrate 201. The memory deviceelements 203 may be transistors such as complementarymetal-oxide-semiconductor transistors, metal-oxide-semiconductorfield-effect transistors, fin field-effect-transistors, the like, or acombination thereof.

With reference to FIG. 3 , the second dielectric layer 207 may be formedon the second substrate 201. In some embodiments, the second dielectriclayer 207 may be a stacked layer structure. The second dielectric layer207 may include a plurality of insulating sub-layers. Each of theinsulating sub-layers may have a thickness between about 0.5 μm andabout 3.0 μm. The insulating sub-layers may be formed of, for example,silicon oxide, borophosphosilicate glass, undoped silicate glass,fluorinated silicate glass, low-k dielectric materials, the like, or acombination thereof. The insulating sub-layers may be formed ofdifferent materials but are not limited thereto.

The insulating sub-layers may be formed by deposition processes such aschemical vapor deposition, plasma-enhanced chemical vapor deposition, orthe like. Planarization processes may be performed after the depositionprocesses to remove excess material and provide a substantially flatsurface for subsequent processing steps.

With reference to FIG. 3 , the second conductive features 205 may beformed in the second dielectric layer 207. The second conductivefeatures 205 may include second conductive lines 205L, second conductivevias 205V, and second conductive pads 205P. The second conductive lines205L may be separated from each other and may be horizontally disposedin the second dielectric layer 207 along the direction Z. In the presentembodiment, the topmost second conductive lines 205L may be designatedas the second conductive pads 205P. The top surfaces of the secondconductive pads 205P and the top surface of the second dielectric layer207 may be substantially coplanar. The second conductive vias 205V mayconnect adjacent second conductive lines 205L along the direction Z,adjacent memory device element 203 and second conductive line 205L, andadjacent second conductive pad 205P and second conductive line 205L. Insome embodiments, the second conductive features 205 may be formed of,for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum,ruthenium, copper, metal carbides (e.g., tantalum carbide, titaniumcarbide, tantalum magnesium carbide), metal nitrides (e.g., titaniumnitride), transition metal aluminides, or a combination thereof. Thesecond conductive features 205 may be formed during the formation of thesecond dielectric layer 207.

With reference to FIG. 3 , the storage units 209 may be formed in thesecond dielectric layer 207 and above the memory cell area MCA. Each ofthe storage units 209 may include an insulator-conductor-insulatorstructure and may be electrically coupled to the corresponding secondconductive pads 205P and the corresponding memory device elements 203,respectively and correspondingly.

In some embodiments, the memory device elements 203, the secondconductive features 205, and the storage units 209 may togetherconfigure functional units of the memory die 200. In some embodiments,the functional units of the memory die 200 may only include core storagecircuitry such as I/O and clocking circuit. The functional units of thememory die 200 may not include any control circuit or high-speedcircuitry.

With reference to FIG. 3 , the top surface of the second dielectriclayer 207 may be referred to as the front surface 200F of the memory die200. The bottom surface of the second substrate 201 may be referred toas the back surface 200B of the memory die 200.

With reference to FIGS. 1, 4, and 5 , at step S15, the memory die 200may be bonded onto the logic die 100, and a thinning process may beperformed to the memory die 200.

With reference to FIG. 4 , the memory die 200 may be flipped. The frontsurface 200F of the memory die 200 may be bonded onto the front surface100F of the logic die 100. That is, the memory die 200 and the logic die100 are bonded in a face-to-face manner. In some embodiments, the memorydie 200 and the logic die 100 may be bonded through a hybrid bondingprocess. In some embodiments, the hybrid bonding process such asthermo-compression bonding, passivation-capping-layer assisted bonding,or surface activated bonding. In some embodiments, the process pressureof the hybrid bonding process may be between about 100 MPa and about 150MPa. In some embodiments, the process temperature of the hybrid bondingprocess may be between about room temperature (e.g., 25° C.) and about400° C. In some embodiments, surface treatments such as wet chemicalcleaning and gas/vapor-phase thermal treatments may be used to lower theprocess temperature of the hybrid bonding process or to short the timeconsuming of the hybrid bonding process. In some embodiments, the hybridbonding process may include, for example, dielectric-to-dielectricbonding, metal-to-metal bonding, and metal-to-dielectric bonding.

In some embodiments, the dielectric-to-dielectric bonding may originatefrom the bonding between the first dielectric layer 107 and the seconddielectric layer 207. The metal-to-metal bonding may originate from thebonding between the first conductive pads 105P and the second conductivepads 205P. The metal-to-dielectric bonding may originate from thebonding between the first conductive pads 105P and the second dielectriclayer 207 and between the second conductive pads 205P and the firstdielectric layer 107.

In some embodiments, a thermal annealing process may be performed afterthe bonding process to enhance dielectric-to-dielectric bonding and toinduce thermal expansion of metal-to-metal bonding so as to furtherimprove the bonding quality.

In some embodiments, the bonding process of the logic die 100 and thememory die 200 may be assisted with a carrier but is not limitedthereto.

With reference to FIG. 5 , the second substrate 201 of the memory die200 may be thinning through a thinning process using wafer grinding,mechanical abrasion, polishing, or the like, or using chemical removal,such as a wet etch. In some embodiments, the thinning process of thememory die 200 may be assisted with a carrier but is not limitedthereto. After the thinning process, the thickness T2 of the secondsubstrate 201 may be between about 5 μm and 100 μm.

With reference to FIGS. 1, 6, and 7 , at step S17, a first inter-die via401 may be formed along the memory die 200 and extending to the logicdie 100.

With reference to FIGS. 6 and 7 , the first inter-die via 401 may beformed along the second substrate 201 and the second dielectric layer207, extending to the first dielectric layer 107, disposed on thecorresponding first conductive line 105L, and electrically connected tothe corresponding first conductive line 105L. In some embodiments, thefirst inter-die via 401 may be formed along the second substrate 201 andthe second dielectric layer 207, disposed on the corresponding firstconductive pad 105P, and electrically connected to the correspondingfirst conductive pad 105P (not shown).

In some embodiments, the first inter-die via 401 may include a fillerlayer FL, a seed layer SL, an adhesion layer AL, a barrier layer BL, andan isolation layer IL.

With reference to FIG. 7 , in some embodiments, the filler layer FL maybe formed along the second substrate 201 and the second dielectric layer207, extending to the first dielectric layer 107, disposed on thecorresponding first conductive line 105L, and electrically connected tothe corresponding first conductive line 105L. The filler layer FL may beformed of, for example, doped polysilicon, tungsten, copper, carbonnanotube, or solder alloy.

In some embodiments, the isolation layer IL may be formed between thefiller layer FL and the second substrate 201, between the filler layerFL and the second dielectric layer 207, between the filler layer FL andthe first dielectric layer 107, and formed on the first conductive line105L. In some embodiments, the isolation layer IL may be formed of, forexample, silicon oxide, silicon nitride, silicon oxynitride, ortetra-ethyl ortho-silicate. The isolation layer IL may have a thicknessbetween about 50 nm and about 200 nm. In some embodiments, the isolationlayer IL may be formed of, for example, parylene, epoxy, orpoly(p-xylene). The isolation layer IL may have a thickness betweenabout 1 μm and about 5 μm. The isolation layer IL may ensure the fillerlayer FL is electrically isolated in the memory die 200 and the logicdie 100.

With reference to FIG. 7 , in some embodiments, the seed layer SL mayhave a U-shaped cross-sectional profile. The seed layer SL may be formedbetween the filler layer FL and the isolation layer IL. In someembodiments, the seed layer SL may have a thickness between about 10 nmand about 40 nm. In some embodiments, the seed layer SL may be formedof, for example, copper. The seed layer SL may reduce a resistivity ofan opening during the formation of the filler layer FL.

With reference to FIG. 7 , in some embodiments, the adhesion layer ALmay have a U-shaped cross-sectional profile. The adhesion layer AL maybe formed between the seed layer SL and isolation layer IL. The seedlayer SL may be formed of, for example, titanium, tantalum, titaniumtungsten, or manganese nitride. The seed layer SL may improve anadhesion between the seed layer SL and the barrier layer BL.

With reference to FIG. 7 , in some embodiments, the barrier layer BL mayhave a U-shaped cross-sectional profile. The barrier layer BL may bebetween the adhesion layer AL and the isolation layer IL. The barrierlayer BL may be formed of, for example, tantalum, tantalum nitride,titanium, titanium nitride, rhenium, nickel boride, or tantalumnitride/tantalum bilayer. The barrier layer BL may inhibit diffusion ofthe conductive materials of the filler layer FL into the secondsubstrate 201, the second dielectric layer 207, and the first dielectriclayer 107.

With reference to FIG. 1 and FIGS. 8 to 10 , at step S19, an interveningstructure 500 may be formed on the memory die 200, and a landing pad 503may be formed in the intervening structure 500 and on the firstinter-die via 401. In some embodiments, the intervening structure 500includes a first layer 501A positioned on the memory die 200, a secondlayer 501B positioned on the first layer 501A, and a third layer 501Cpositioned on the second layer 501B.

In some embodiments, the first layer 501A and the second layer 501Cinclude the same material, while the second layer 501B includes materialdifferent from the first layer 501A. In some embodiments, the firstdielectric layer includes silicon oxide or silicon nitride, the secondlayer 501B includes silicon, and the third layer includes silicon oxideor silicon nitride.

With reference to FIG. 8 , the intervening structure 500 may be formedon the second substrate 201. In some other embodiments, the interveningstructure 500 may be a dielectric layer. The dielectric layer mayinclude a nitride such as silicon nitride, an oxide such as siliconoxide, an oxynitride such as silicon oxynitride, silicon nitride oxide,phosphosilicate glass, borosilicate glass, boron-doped phosphosilicateglass, or the like, or a combination thereof. In some embodiments, theintervening structure 500 may include polybenzoxazole, polyimide,benzocyclobutene, ajinomoto buildup film, solder resist film, the like,or a combination thereof. The intervening structure 500 formed ofpolymeric material may have a number of attractive characteristics suchas the ability to fill openings of high aspect ratio, a relatively lowdielectric constant (about 3.2), a simple depositing process, thereduction of sharp features or steps in the underlying layer, and hightemperature tolerance after curing.

In some embodiments, the intervening structure 500 may be formed by, forexample, spin-coating, lamination, deposition, or the like. Thedeposition may include chemical vapor deposition such as plasma-enhancedchemical vapor deposition. The process temperature of theplasma-enhanced chemical vapor deposition may be between about 350° C.and about 450° C. The process pressure of the plasma-enhanced chemicalvapor deposition may be between about 2.0 Torr and about 2.8 Torr. Theprocess duration of the plasma-enhanced chemical vapor deposition may bebetween about 8 seconds and about 12 seconds.

With reference to FIGS. 9 and 10 , a landing pad opening 501O may beformed in the intervening structure 500 and a conductive material may beformed to fill the landing pad opening 501O to form the landing pad 503.The landing pad opening 501O may be formed by a photolithography processand a subsequent etching process. The first inter-die via 401 may beexposed through the landing pad opening 501O. After the filling of theconductive material, a planarization process, such as chemicalmechanical polishing, may be performed to remove excess material andprovide a substantially flat surface for subsequent processing steps.The conductive material may be, for example, copper or other applicableconductive materials.

With reference to FIGS. 1 and 11 , at step S21, a sensor die 300 may beprovided.

With reference to FIG. 11 , the sensor die 300 may include a thirdsubstrate 301, a plurality of sensor device elements 303, a pluralitysensor conductive features 305, and a third dielectric layer 307.

With reference to FIG. 11 , the third substrate 301 may be formed of asemiconductor or compound semiconductor. For example, the thirdsubstrate 301 may include silicon, germanium, silicon carbide, galliumarsenide, indium arsenide, or indium phosphide. The third substrate 301may include a conductive region, for example, a well in which animpurity is doped, or a structure doped with an impurity. Also, thethird substrate 301 may have various isolation structures, for example,a shallow trench isolation structure or a deep trench isolationstructure.

In some embodiments, the thickness T3 of the third substrate 301 may bebetween about 500 μm and about 700 μm. For example, the thickness T3 ofthe third substrate 301 may be about 600 μm.

With reference to FIG. 11 , the third substrate 301 may include a sensorpixel area SCA and a sensor peripheral area SPA. In some embodiments,the sensor peripheral area SPA may be next to the sensor pixel area SCA.In some embodiments, in a top-view perspective (not shown), the sensorpixel area SCA may be the central region of the third substrate 301. Thesensor peripheral area SPA may be the peripheral region of the thirdsubstrate 301 which is surrounding the central region.

With reference to FIG. 11 , the sensor device elements 303 may be formedon the third substrate 301. Some portions of the sensor device elements303 may be formed in the third substrate 301. In some embodiments, thesensor device elements 303 may include transfer gates 303G, sensor units303S, floating diffusion units 303F, and transistors such ascomplementary metal-oxide-semiconductor transistors,metal-oxide-semiconductor field-effect transistors, finfield-effect-transistors.

For brevity, clarity, and convenience of description, only one transfergate 303G, one sensor unit 303S, and one floating diffusion unit 303Fare described. In some embodiments, the transfer gate 303G, the sensorunit 303S, and the floating diffusion unit 303F are located at thesensor pixel area SCA. In some embodiments, the sensor unit 303S may bea photodiode and may be electrically coupled to the source of thetransfer gate 303G. The floating diffusion unit 303F may be formed inthe third substrate 301, for example, through implanting into substrateto form a p-n junction. In some embodiments, the floating diffusion unit303F may be formed in the drain 303D of the transfer gate 303G. That is,the floating diffusion unit 303F may be electrically coupled to thedrain 303D of the transfer gate 303G. In some embodiments, the othertransistors may be configured as row selectors, source followers, andreset transistors.

With reference to FIG. 11 , the third dielectric layer 307 may be formedon the third substrate 301. In some embodiments, the third dielectriclayer 307 may be a stacked layer structure. The third dielectric layer307 may include a plurality of insulating sub-layers. Each of theinsulating sub-layers may have a thickness between about 0.5 μm andabout 3.0 μm. The insulating sub-layers may be formed of, for example,silicon oxide, borophosphosilicate glass, undoped silicate glass,fluorinated silicate glass, low-k dielectric materials, the like, or acombination thereof. The insulating sub-layers may be formed ofdifferent materials but are not limited thereto.

With reference to FIG. 11 , the sensor conductive features 305 may beformed in the third dielectric layer 307. The sensor conductive features305 may be electrically coupled to the sensor device elements 303,respectively and correspondingly. The sensor conductive features 305 mayinclude third conductive lines 305L, third conductive vias 305V, andthird conductive pads 305P. The third conductive lines 305L may beseparated from each other and may be horizontally disposed in the thirddielectric layer 307 along the direction Z. In the present embodiment,the topmost third conductive lines 305L may be designated as the thirdconductive pads 305P. The top surfaces of the third conductive pads 305Pand the top surface of the third dielectric layer 307 may besubstantially coplanar. The third conductive vias 305V may connectadjacent third conductive lines 305L along the direction Z, adjacentsensor device element 303 and third conductive line 305L, and adjacentthird conductive pad 305P and third conductive line 305L. In someembodiments, the sensor conductive features 305 may be formed of, forexample, tungsten, cobalt, zirconium, tantalum, titanium, aluminum,ruthenium, copper, metal carbides (e.g., tantalum carbide, titaniumcarbide, tantalum magnesium carbide), metal nitrides (e.g., titaniumnitride), transition metal aluminides, or a combination thereof. Thesensor conductive features 305 may be formed during the formation of thethird dielectric layer 307.

With reference to FIG. 11 , the top surface of the third dielectriclayer 307 may be referred to as the front surface 300F of the sensor die300. The bottom surface of the sensor die 300 may be referred to as theback surface 300B of the sensor die 300.

With reference to FIGS. 1 and 12 , at step S23, the sensor die 300 maybe bonded onto the intervening structure 500.

With reference to FIG. 12 , the sensor die 300 may be flipped. The frontsurface 300F of the sensor die 300 may be bonded onto the interveningstructure 500 through a bonding process. In some embodiments, thebonding process may be an oxide bonding process through thedielectric-to-dielectric bonding originated form the third dielectriclayer 307 and the intervening structure 500.

With reference to FIGS. 1, 13, and 14 , at step S25, a thinning processmay be performed to the sensor die 300, a first intra-die via 403 may beformed in the sensor die 300, and a second intra-die via 405 may beformed in the sensor die 300.

With reference to FIG. 13 , the third substrate 301 of the sensor die300 may be thinned through a thinning process using wafer grinding,mechanical abrasion, polishing, or the like, or using chemical removal,such as a wet etch. In some embodiments, the thinning process of thesensor die 300 may be assisted with a carrier but is not limitedthereto. After the thinning process, the thickness T3 of the thirdsubstrate 301 may be between about 5 μm and 100 μm. With the thirdsubstrate 301 having a small thickness, light may penetrate from backsurface 300B into third substrate 301, and reach sensor unit 303S.

With reference to FIG. 14 , the first intra-die via 403 may be formedalong the third substrate 301 and the third dielectric layer 307, and onthe landing pad 503. The first intra-die via 403 may be electricallyconnected to the landing pad 503. That is, the first intra-die via 403may be electrically coupled to the logic die 100 through the landing pad503 and the first inter-die via 401. The second intra-die via 405 may beformed along the third substrate 301, extending to the third dielectriclayer 307, and on the corresponding third conductive line 305L. Theheight D1 of the first intra-die via 403 may be greater than the heightD2 of the second intra-die via 405. In some embodiments, the heightratio of the height D1 of the first intra-die via 403 to the height D2of the second intra-die via 405 may be between about 10:3 and about 5:4.In some embodiments, the first intra-die via 403 and the secondintra-die via 405 may be electrically coupled to each other.

In some embodiments, the first intra-die via 403 and the secondintra-die via 405 may have structures similar to the first inter-die via401, and descriptions thereof are not repeated herein.

With reference to FIGS. 1 and 15 , at step S27, an upper layer 505 maybe formed on the sensor die 300, a plurality of color filters 507 may beformed on the upper layer 505, and a plurality of micro-lenses 509 maybe formed on the plurality of color filters 507.

With reference to FIG. 15 , the upper layer 505 may be formed on thesensor pixel area SCA. The upper layer 505 may cover the sensor units303S in a top-view perspective (not shown). In some embodiments, theupper layer 505 may include one or more of a bottom anti-reflectivecoating, a silicon oxide layer, and a silicon nitride layer.

With reference to FIG. 15 , the color filters 507 may include, forexample, a red filter, a blue filter, and a green filter. In someembodiments, the color filters 507 may include a cyan filter, a yellowfilter, and a magenta filter. The color filter 507 may betopographically aligned with the corresponding sensor unit 303S. Thesensor unit 303S may detect components of incident light that areseparated from each other to realize the color. The micro-lenses 509 mayconcentrate incident light in the sensor pixel area SCA on the sensorunit 303S. When the sensor units 303S include photodiodes, themicro-lenses 509 may concentrate incident light in the sensor pixel areaSCA on the photodiodes.

It should be noted that, in the description of the present disclosure,an x-y-z coordinate system is assumed where x and y refer to directions(dimensions) within the plane parallel to the major surface of thestructure and z refers a direction (dimension) perpendicular to theplane, two features are topographically aligned when those features havesubstantially the same x, y coordinates.

With reference to FIG. 15 , the logic die 100, the memory die 200, thesensor die 300, the first inter-die via 401, the first intra-die via403, the second intra-die via 405, the intervening structure 500, thelanding pad 503, the upper layer 505, the color filters 507, and themicro-lenses 509 together configure the optical semiconductor device 1A.

In some embodiments, the optical semiconductor device 1A may beconfigured as an optical sensor device to detect images. The sensor unit303S (e.g., photodiode) may receive light (for example, visible rays orinfrared rays) from the outside and may produce photocharges based onthe received light. The photocharges produced by the sensor unit 303Smay be transferred to the floating diffusion unit 303F via the channelof the transfer gate 303G and the photocharges produced by the sensorunit 303S may be stored in the floating diffusion unit 303F.

In some embodiments, the reset transistor of the sensor die 300 mayreceive a reset signal. When the reset signal is activated, the chargesaccumulated in the floating diffusion unit 303F may be discharged toreset the floating diffusion unit 303F.

In some embodiments, the functional units of the logic die 100 mayperform various operations to provide a digital image signal from theimages captured by the optical semiconductor device 1A. For example,various post processing algorithms may be executed by the logic die 100.Examples of the post processing algorithms included but are not limitedto contrast enhancement, sharpness enhancement, or noise reduction. Anoutput from the logic die 100 may be supplied by a video codecprocessor. An image processed by the video codec processor may be outputto the display or stored in the memory die 200.

By employing the first inter-die via 401, the first intra-die via 403,and the second intra-die via 405, the signal produced in the sensor die300 may be transferred to the functional circuits of the logic die 100to perform various processing which usually needs complicated circuits.In other words, the sensor die 300 can only reserve the essentialelements for optical sensing function to simplify the complexity offabrication of the sensor die 300. As a result, the yield of the opticalsemiconductor device 1A may be improved. In addition, the firstinter-die via 401, the first intra-die via 403, and the second intra-dievia 405 may also shorten the signal path between the function circuitsof different dies so that the energy consumption for signal transferringmay be reduced. Furthermore, by further integrating the memory die 200,the intermediate processing or the post processing signal may be easilystored.

In some embodiments, the bonding of the logic die 100, the memory die200, and the sensor die 300 may be at wafer level. In the wafer-levelbonding, wafers, which may include the logic die 100, the memory die200, and the sensor die 300, respectively, may be bonded together, andmay then sawed into dies. Alternatively, the bonding may be performed atthe chip level.

FIG. 16 illustrates, in a schematic cross-sectional view diagram, anoptical semiconductor device 1B in accordance with another embodiment ofthe present disclosure.

With reference to FIG. 16 , the optical semiconductor device 1B may havea structure similar to that illustrated in FIG. 15 . The same or similarelements in FIG. 16 as in FIG. 15 have been marked with similarreference numbers and duplicative descriptions have been omitted. Theoptical semiconductor device 1B may include a plurality of assistanceconductive pads 511 disposed in the intervening structure 500 andcontacting the third conductive pads 305P, respectively andcorrespondingly. The assistance conductive pads 511 may be formed of,for example, tungsten, cobalt, zirconium, tantalum, titanium, aluminum,ruthenium, copper, metal carbides (e.g., tantalum carbide, titaniumcarbide, tantalum magnesium carbide), metal nitrides (e.g., titaniumnitride), transition metal aluminides, or a combination thereof. Theassistance conductive pads 511 may improve the bonding strength betweenthe intervening structure 500 and the sensor die 300 by providingadditional metal-to-metal bondings.

FIGS. 17 and 18 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device 1C inaccordance with another embodiment of the present disclosure.

With reference to FIG. 17 , an intermediate optical semiconductor devicemay be fabricated with a procedure similar to that illustrated in FIGS.2 to 12 , and descriptions thereof are not repeated herein. The firstsubstrate 101 of the logic die 100 may be thinned through a thinningprocess using wafer grinding, mechanical abrasion, polishing, or thelike, or using chemical removal, such as a wet etch. In someembodiments, the thinning process of the first substrate 101 may not beperformed with a carrier. The memory die 200, the intervening structure500, and the sensor die 300 may serve as a temporary carrier to preventthe logic die 100 from breaking even through the logic die 100 has asmall thickness during and after the thinning process of the firstsubstrate 101. After the thinning process, the thickness T1 of the firstsubstrate 101 may be between about 5 μm and 100 μm or less than about 10μm.

With reference to FIG. 18 , the thinning process of the third substrate301, the fabrication of the first intra-die via 403, the secondintra-die via 405, the upper layer 505, the color filters 507, and themicro-lenses 509 may be similar to a procedure that illustrates in FIGS.13 to 15 , and descriptions thereof are not repeated herein. Because acarrier is not necessary during the thinning process of the firstsubstrate 101, the cost and process complexity of fabricating theoptical semiconductor device 1C may be reduced.

FIGS. 19 to 21 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device 1D inaccordance with another embodiment of the present disclosure.

With reference to FIG. 19 , an intermediate optical semiconductor devicemay be fabricated with a procedure similar to that illustrated in FIGS.2 to 6 , and descriptions thereof are not repeated herein. The sensordie 300 may be provided as illustrated in FIG. 11 , and descriptionsthereof are not repeated herein. The sensor die 300 may be flipped andbonded onto the memory die 200 directly.

With reference to FIG. 20 , the third substrate 301 may be thinned witha process similar to that illustrated in FIG. 13 , and descriptionsthereof are not repeated herein. The first intra-die via 403 may beformed along the third substrate 301 and the third dielectric layer 307,and directly on the first inter-die via 401. In other words, the firstinter-die via 401 and the first intra-die via 403 are topographicallyaligned and the first inter-die via 401 and the first intra-die via 403are electrically connected. The second intra-die via 405 may be formedwith a procedure similar to that illustrated in FIG. 14 , anddescriptions thereof are not repeated herein.

With reference to FIG. 21 , the upper layer 505, the color filters 507,and the micro-lenses 509 may be formed with a procedure similar to thatillustrated in FIG. 15 , and descriptions thereof are not repeatedherein.

FIGS. 22 to 29 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device 1E inaccordance with another embodiment of the present disclosure.

With reference to FIG. 22 , the logic die 100 may be provided asillustrated in FIG. 2 . Above the logic peripheral circuit area LPA, oneof the first conductive lines 105L, one of the first conductive vias105V, and one of the first conductive pads 105P may be topographicallyaligned. In other words, the first conductive line 105L, the firstconductive via 105V, and the first conductive via pad 105P arevertically arranged along the direction Z.

With reference to FIG. 23 , the memory die 200 may be provided asillustrated in FIG. 3 . Above the memory peripheral area MPA, one of thesecond conductive via 205V and one of the second conductive pad 205P maybe topographically aligned. In other words, the second conductive via205V and the second conductive pad 205P are vertically arranged alongthe direction Z.

With reference to FIG. 24 , the logic die 100 and the memory die 200 maybe bonded in a face-to-face manner with a procedure similar to thatillustrated in FIG. 4 . After bonding, the second conductive via 205Vand the second conductive pad 205P located at the memory peripheral areaMPA may topographically aligned with the first conductive line 105L, thefirst conductive via 105V, and the first conductive pad 105P located atthe logic peripheral circuit area LPA. That is, at the logic peripheralcircuit area LPA and at the memory peripheral area MPA, the firstconductive line 105L, the first conductive via 105V, the firstconductive pad 105P, the second conductive pad 205P, and the secondconductive via 205V are vertically arranged along the direction Z andtogether configure the first inter-die via 401 which can communicate thememory die 200 and the logic die 100.

With reference to FIG. 25 , the second substrate 201 of the memory die200 may be thinned with a procedure similar to that illustrated in FIG.5 , and descriptions thereof are not repeated herein. The landing pad503 may be formed in the second substrate 201 and on the first inter-dievia 401.

With reference to FIG. 26 , the sensor die 300 may be provided asillustrated in FIG. 11 , and descriptions thereof are not repeatedherein. The sensor die 300 may be flipped and bonded on the memory die200 directly.

With reference to FIGS. 27 to 29 , the thinning process of the thirdsubstrate 301, the fabrication of the first intra-die via 403, thesecond intra-die via 405, the upper layer 505, the color filters 507,and the micro-lenses 509 may be similar to a procedure that illustratesin FIGS. 13 to 15 , and descriptions thereof are not repeated herein.

FIGS. 30 and 31 are schematic cross-sectional view diagrams illustratingpart of a flow for fabricating the optical semiconductor device 1F inaccordance with another embodiment of the present disclosure.

With reference to FIG. 30 , an intermediate optical semiconductor devicemay be fabricated with a procedure similar to that illustrates in FIGS.22 to 26 , and descriptions thereof are not repeated herein. The firstsubstrate 101 of the logic die 100 may be thinned through a thinningprocess using wafer grinding, mechanical abrasion, polishing, or thelike, or using chemical removal, such as a wet etch. In someembodiments, the thinning process of the first substrate 101 may not beperformed with a carrier. The memory die 200 and the sensor die 300 mayserve as a temporary carrier to prevent the logic die 100 from breakingeven through the logic die 100 has a small thickness during and afterthe thinning process of the first substrate 101. After the thinningprocess, the thickness T1 of the first substrate 101 may be betweenabout 5 μm and 100 μm or less than about 10 μm.

With reference to FIG. 31 , the thinning process of the third substrate301, the fabrication of the first intra-die via 403, the secondintra-die via 405, the upper layer 505, the color filters 507, and themicro-lenses 509 may be similar to a procedure illustrated in FIGS. 13to 15 , and descriptions thereof are not repeated herein. Because acarrier is not necessary during the thinning process of the firstsubstrate 101, the cost and process complexity of fabricating theoptical semiconductor device 1F may be reduced.

One aspect of the present disclosure provides an optical semiconductordevice including a logic die including a core circuit area and a logicperipheral circuit area; a memory die positioned on the logic die andincluding a memory cell area and a memory peripheral area, and a firstinter-die via positioned in the memory peripheral area and electricallyconnected to the logic peripheral circuit area; and a sensor diepositioned on the memory die and including a sensor pixel area and asensor peripheral area, a first intra-die via positioned in the sensorperipheral area and electrically coupled to the logic peripheral circuitarea through the first inter-die via, and a second intra-die viapositioned in the sensor peripheral area. A height of the firstintra-die via is greater than a height of the second intra-die via.

Another aspect of the present disclosure provides an opticalsemiconductor device including a logic die including a front surface; amemory die including a front surface positioned on the front surface ofthe logic die, and a back surface opposite to the front surface of thememory die; and a sensor die including a front surface positioned on theback surface of the memory die, a back surface opposite to the frontsurface of the sensor die, a sensor unit located at the back surface ofthe sensor die, a color filter positioned on the back surface of thesensor die, and a micro-lens positioned on the color filter.

Another aspect of the present disclosure provides an opticalsemiconductor device including a logic die including a core circuit areaand a logic peripheral circuit area; a memory die positioned on thelogic die and including a memory cell area and a memory peripheral area;a first inter-die via positioned in the memory peripheral area; alanding pad positioned on the first inter-die via; and a sensor diepositioned on the memory die and including a sensor pixel area and asensor peripheral area, a first intra-die via positioned in the sensorperipheral area. The first inter-die via and the first intra-die via areelectrically coupled through the landing pad in a cascade manner.

Due to the design of the optical semiconductor device of the presentdisclosure, by employing the first inter-die via 401, the firstintra-die via 403, and the second intra-die via 405, the signal producedin the sensor die 300 may be transferred to the functional circuits ofthe logic die 100 to perform various processing which usually needscomplicated circuits. That is, the sensor die 300 can only reserve theessential elements for optical sensing function so that the complexityof fabrication of the sensor die 300 may be simplified. As a result, theyield of the optical semiconductor device 1A may be improved. Inaddition, the first inter-die via 401, the first intra-die via 403, andthe second intra-die via 405 may also shorten the signal path betweenthe function circuits of different dies so that the energy consumptionfor signal transferring may be reduced. Furthermore, by furtherintegrating the memory die 200, the intermediate processing or the postprocessing signal may be easily stored.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the appended claims. For example,many of the processes discussed above can be implemented in differentmethodologies and replaced by other processes, or a combination thereof.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present disclosure, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present disclosure. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, and steps.

What is claimed is:
 1. An optical semiconductor device, comprising: alogic die comprising a front surface; a memory die comprising: a frontsurface positioned on the front surface of the logic die; and a backsurface opposite to the front surface of the memory die; and a sensordie comprising: a front surface positioned on the back surface of thememory die; a back surface opposite to the front surface of the sensordie; a substrate defining the back surface of the sensor die thereat; adielectric layer defining the front surface of the sensor die thereatand coupling at the substrate; and a sensor unit located in thesubstrate at a front surface thereof, a color filter positioned on theback surface of the sensor die; a micro-lens positioned on the colorfilter; a first inter-die via positioned in a memory peripheral area ofthe memory die, wherein the first inter-die via has a first end extendedat the back surface of the memory die and an opposed second end extendedinto the logic die through the front surface of the memory die, suchthat a height of the first inter-die via between the first and secondends thereof is larger than a thickness of the memory die between thefront and back surfaces thereof; a first intra-die via positioned in asensor peripheral area of the sensor die, wherein the first intra-dievia has a first end extended at the back surface of the sensor die andan opposed second end extended at the front surface of the sensor die,wherein a height of the first intra-die via between the first and secondends thereof equals to a thickness of the sensor die between the frontand back surfaces thereof, wherein a width of the first intra-die via isgradually reduced from the first end of the first intra-die via to thesecond end thereof, wherein the first end of the first inter-die via iselectrically coupled to the second end of first intra-die via; a secondintra-die via positioned in a sensor peripheral area of the sensor die,wherein the second intra-die via has a first end extended at the backsurface of the sensor die and an opposed second end extended toward thefront surface of the sensor die, such that a height of the secondintra-die via between the first and second ends thereof is smaller thanthe height of the first intra-die via, wherein a width of the secondintra-die via is gradually reduced from the first end of the secondintra-die via to the second end thereof, wherein the first end of thesecond intra-die via is spaced apart from the first end of the firstintra-die via; an intervening structure serving as an insulating layerand having a front surface contacting with the back surface of thememory die and an opposed back surface contacting with the front surfaceof the sensor die, wherein the intervening structure has a landing padopening; a landing pad disposed at the landing pad opening; and whereinthe first inter-die via and the first intra-die via are electricallycoupled through the landing pad in a cascade manner, such that the firstend of the first inter-die via is electrically coupled at the frontsurface of the intervening structure while the second end of the firstintra-die via is electrically coupled at the back surface of theintervening structure.
 2. The optical semiconductor device of claim 1,wherein the sensor unit, the color filter, and the micro-lens aretopographically aligned, wherein the first end of the first inter-dievia is aligned with the second end of the first intra-die via, such thatthe first inter-die via is electrically coupled to the first intra-dievia end-to-end, wherein the width of the first end of the firstinter-die via is greater than the width of the second end of the firstintra-die via.
 3. The optical semiconductor device of claim 2, furthercomprising an upper layer formed on the back surface of the sensor die,wherein a width of the upper layer is smaller than a width of the sensordie to uncover the first end of first intra-die via, wherein the upperlayer is sandwiched between the sensor die and the color filter; whereinthe upper layer comprises a bottom anti-reflective coating.
 4. Theoptical semiconductor device of claim 3, wherein the sensor unit is aphotodiode, wherein a width of the first inter-die via is graduallyreduced from the first end of the first inter-die via to the second endthereof.
 5. The optical semiconductor device of claim 1, wherein thefirst inter-die via and the first intra-die via are not topographicallyaligned, such that the first end of the first inter-die via ismisaligned with the second end of the first intra-die via, wherein thelanding pad opening is a through opening extended from the front surfaceof the intervening structure and the back surface thereof, such that athickness of the landing pad equals to a thickness of the interveningstructure.
 6. The optical semiconductor device of claim 5, wherein thefirst inter-die via is electrically connected to a peripheral circuitarea of the logic die.
 7. The optical semiconductor device of claim 6,wherein the dielectric layer is positioned on the intervening structureto cover the landing pad opening, wherein the first intra-die via ispositioned penetrating along the substrate of the sensor die and thedielectric layer of the sensor die, and positioned on the landing pad.8. The optical semiconductor device of claim 7, further comprising atransfer gate in the dielectric layer of the sensor die.
 9. The opticalsemiconductor device of claim 8, further comprising a floating diffusionunit positioned in the substrate of the sensor die and positioned in adrain of the transfer gate.
 10. The optical semiconductor device ofclaim 9, wherein the color filter is positioned on the substrate of thesensor die and above the sensor unit.
 11. The optical semiconductordevice of claim 10, wherein the micro-lens is positioned on the colorfilter.
 12. The optical semiconductor device of claim 11, furthercomprising an upper layer formed on the back surface of the sensor die,wherein a width of the upper layer is smaller than a width of the sensordie to uncover the first end of first intra-die via, wherein the upperlayer is positioned between the color filter and the substrate of thesensor die; wherein the upper layer comprises a bottom anti-reflectivecoating.
 13. The optical semiconductor device of claim 12, wherein theintervening structure comprise a first layer positioned on the memorydie, a second layer positioned on the first layer, and a third layerpositioned on the second layer, wherein at least one of the first,second and third layers is the insulating layer.
 14. The opticalsemiconductor device of claim 13, wherein the sensor unit includes aphotodiode.